1, maybe not use all caps next time, it looks like you are yelling at people.

2, I'd hook up that vent if I were you! When a battery is "working" it vents corrosive gasses... and that isn't good to have in the cabin of the vehicle right by all the electronics. BMW engineers were smart enough to put a vent hose there to redirect the gasses outside the vehicle. I have 3 times in my career at BMW seen electrical problems caused by the vent not being used with aftermarket batteries. Usually on a car model where the battery is right under the rear fuse box, and guess what, that fuse box got severely corroded and needed to be replaced along with some wiring. Expensive job....

And that was actually made worse by the aftermarket battery believe it or not... these vehicles charging systems are computer controlled. So if the OEM battery has 850 CA, 850 CCA, 110AH and 250 RC. and the aftermarket battery has 950 CA it must be better right? Not exactly... that 950 CA battery has only 750 CCA, 90 AH and no listed RC rating. So when the alternator is trying to force more charging amps down it's throat than it is designed to handle it produces more gasses as a result.

I'm not telling you not to use the aftermarket battery, just that you really should hook up the vent hose to prevent costing you electronics. (the self leveling suspension module, PDC, radio if you have nav, trailer module if you have towing, etc. are all right by the battery)

I'm with Weasel...
and the only reason not to hook up the vent tube is if one had an AGM type batt, (usually with no vent tube/hole),
but I don't recall seeing one of those for X5 use.
GL, mD

+1
I can't imagine that toxic fumes can be very good for your health either ;)

Well...... Finally "Switched out my oem 6 yr + old battery today"
Gave a look at Motor David's work and gave it a go.

Since it died in my garage I first decided to give AAA a shot but reneged
on the deal. $146.00 plus tax for a battery that was probably going
to be just fine But somehow i just wasn't comfortable with the process.
Besides before I let someone else start talking stuff apart to get
to the battery I thought "hey you need to know about this yourself".

Turns out that with the AAA discount at the dealer it was a few dollars
more and no doubts about the fit and compatibility. So far all systems
are a go.

Thanks for the info. Unfortunately, I bought my battery at autozone before reading this thread. When they were installing my battery, they told me that the vent hose is not needed. I was curious about its function as every design has a purpose. My question is, what should I do if the battery does not have a vent hole? Should I just poke and create one?

This is the battery that I bought - Gold-Duralast/Battery (H8-DLG) | Battery | 2001 BMW X5 AWD 8 Cylinders 4.4L EFI DOHC | AutoZone.com

markreg,
I have not had that specific batt 'in hand', so I don't know it.
The AZ ad for that batt says:
"BEST IN CLASS VENT CAPS are engineered to be safer and reduce leakage and corrosion."

And, it also states in the fine print specs:
" Battery is vented to outside of vehicle."

So, you or they skipped that vent hole app, or it isn't readily apparent, or that batt is using cap vent system vs a vent tube.
Not an EE or CE, but some would get excited with not having a vent tube vs. cap venting to interior atmosphere, with that
'atmosphere' being your trunk...some would think it a trifle.

I would crawl in and look again for a potential vent tube hole, and Weasel or some of the other knowledgeable tech people may have an opin.
GL, mD

If I remember right the vent opening for the duralast may be in the center of the back of the top, but a bigger hole that requires an extension hose and adapter to hook it up. But I have seen them properly vented in the past through the shop.

Thanks guys! I'll definitely take a look this weekend and will update.

My current AZ duralast does have vent holes on both sides (if I recalled). I pulled the cap off the OEM battery and reuse it on the duralast to plug up the unused side.

X5 battery
 

To anyone considering an aftermarket battery, but is worried about fit, performance, vent tube etc.....

If you have a part #61 21 8 381 762 (as I do in my 2004) the dealer list price for the battery is $144. (not including installation, of course). If they are asking more, try a different dealer, it may be much higher due to "matrix pricing" or part number substitution.

Or you can buy the OEM for $115 if you live near one of these BMW dealers:

http://www.trademotion.com/partlocat...?siteid=214760
getBMWparts.com

No need to worry about aftermarket at these prices..